fIxAçãO PEDICULAR PERCUTÂNEA DE fRATURAS VERTEbRAIS TORACOLOMbARES SEM COMPROMISSO NEUROLógICO PERCUTANEOUS PEDICLE FIxATION OF THORACOLUMBAR VERTEBRAL FRACTURES WITHOUT NEUROLOGICAL DEFICITS

OBJETIVO: Evaluar la eficacia y la seguridad de la fijacion percutanea pedicular de fracturas toracolumbares sin comprometimiento neurologico. METODOS: Se incluyeron en el estudio los pacientes de edades comprendidas entre 18 y 70 anos, con fractura toracolumbar tipo AO (A.3), cifosis >30° o reduccion de la altura del cuerpo vertebral >50% o compresion del canal vertebral >50%, quienes fueron sometidos a tratamiento quirurgico mediante fijacion percutanea pedicular. Se evaluaron los parametros radiologicos: el angulo de Cobb, el colapso vertebral, el acunamiento anterior y la compresion del canal vertebral antes de la operacion, despues de la operacion y al final del seguimiento. La evolucion clinica y funcional fue evaluada por el Oswestry Disability Index (ODI). RESULTADOS: El tiempo quirurgico promedio fue 81 minutos (minimo 69, maximo 95 min.) El volumen promedio de la perdida de sangre intraoperatoria fue 85 ml (minimo 75 y maximo 155 ml). El promedio de seguimiento fue siete meses (minimo 3 meses, maximo 14 meses). Se presento un ODI promedio final de 18% (excelente). CONCLUSIONES: Los resultados clinicos sugieren que la fijacion percutanea pedicular puede ser una tecnica quirurgica alternativa para el tratamiento de las fracturas toracolumbares tipo AO (A.3), sin deficits neurologicos. Esta tecnica ha demostrado ser eficaz y segura, y presenta las ventajas de un enfoque minimamente invasivo.


PERCUTANEOUS PEDICLE FIXATION OF THORACOLUMBAR VERTEBRAL FRACTURES WITHOUT NEUROLOGICAL DEFICITS
The technique of placing pedicle screws percutaneously was initially introduced by Magerl in 1977. 7Kim et al. 8

proved that percutaneous pedicle fixation causes less muscle damage than open pedicle fixation techniques.
The aim of this prospective study was to evaluate the efficacy and safety of percutaneous pedicle fixation using a minimally invasive technique for AO type (A.3) thoracolumbar fractures.

MATERIAL AND METHODS
Inclusion criteria were: AO type (A.3) thoracolumbar fracture; kyphosis > 30° and/or reduction of vertebral body height > 50% and/or compression of the spinal canal > 50%. 9Exclusion criteria were: age less than 18 years or over 70 years, impossibility of surgical treatment in the first ten days after the injury, and the presence of neurological deficits.The study took place between December 2010 and December 2011.Twenty-three adult patients were included in this study, 12 were male and 11 female.The average age was 49.4 years (minimum of 24 and maximum of 68).As for the distribution of fractures by vertebral level, we obtained three cases affecting T8, one T9, one T11, four cases T12, ten L1, two L2, one L3, and one L4.The mechanism of injury included: 20 cases of falling from heights, two pedestrians being run over and one car crash.(Table 1) The pre-and postoperative evaluation during follow-up was performed using radiography (Figure 1) and CAT of the thoracolumbar spine.(Figure 2) The radiological parameters evaluated were the Cobb angle, reduction of the height of the vertebral body, anterior wedging of the fractured vertebra, and compression of the spinal canal.The sagittal curvature was measured by the Cobb angle (defined as the angle between the upper surface of the vertebral body above the fracture and the bottom surface of the vertebral body at the level below the fracture). 10Patients were evaluated at one, three, six, and 12 months postoperatively, clinically, the Oswestry Disability Index was collected, and radiographically and with CAT at three or six months.

Surgical technique
All patients were treated with the CD Horizon Longitude TM system (Medtronic -2600 Sofamor Danek Drive, Memphis, TN 38132).
The patient was under general anesthesia in the prone position with the abdomen uncovered.Identification of the entry point was made with fluoroscopic control.An incision of approximately 2 cm was made in the skin, slightly lateral to the pedicle entry point.We used a dilation tube (smaller diameter) to move soft tissues away from the entry point.The needle/punch, guide wire, and cannulated auger with the appropriate diameter and length (transpedicular) were successively placed under fluoroscopic control.Subsequently, the cannulated screw was placed through the dilator.This sequence of steps was repeated for each screw.Rods of suitable lengths were placed and shaped, as necessary, by a cranial incision, with the help of a guide.(Figure 3) Subsequent to the placement of the rods, we proceeded to distract and lock them.A control image was performed to check A B the positioning of screws, rods, and the restoration of the sagittal alignment.The dilators were removed, and the skin was closed.
Postoperatively, the patients received antibiotic prophylaxis for 48 hours.The patient was allowed to stand after 24 hours and return to daily activities within two weeks.
The average clinical evaluation with the Oswestry disability index was 18% (excellent).Of the 23 patients treated, 19 showed no disabilities (0-20%), and four had moderate disability (21-40%).None showed a worsening of neurological status, infection, or fixation failure.

RESULTS
All patients were treated with percutaneous pedicle fixation.The mean operative time was 81 minutes (minimum of 69, maximum of 95).The mean intraoperative blood loss was 85 ml (minimum of 75, maximum of 155 ml).Hospitalization time was on average seven days (minimum of 5, maximum of 11 days).All patients were followed up as outpatients for an average period of seven months (minimum of three, maximum of 14 months).The preoperative Cobb angle averaged 16.9° (5.3°-31.7°),postoperatively it was 4.9°, which represents an improvement of about 86%.(Figure 4 and 5) At the end of follow-up it was 8.2°.The percentage of mean preoperative reduction of the vertebral body height was 39.8% (31.6% to 61.6%) and 10.3% postoperatively, representing an improvement of about 29.5%.At the final follow-up visit, it was 13.2%.The percentage of mean preoperative anterior wedging of the vertebral body was 37.4% (27.1% to 57.2%) and 20.3% postoperatively, representing an improvement of about 17 1%.At the final follow-up visit, it was 24.1%.The percentage of compression of the spinal canal was 28.5% (8.4 to 53.8).At the final follow-up visit, it was 13.9%.(Table 2)

DISCUSSION
The first descriptions of the use of plates and pedicle screws to treat thoracolumbar fractures appeared in 1963. 11This kind of fixation with the open posterior approach is associated with a high morbidity and extensive damage to the paravertebral muscle.On the other hand, minimally invasive approaches, such as percutaneous pedicle fixation, dramatically decreased the extent of iatrogenic muscle injury.
Kim et al. 8 demonstrated that percutaneous pedicle fixation causes less damage to the paravertebral muscle than open fixation techniques.
In a multicenter, prospective, randomized study, Siebenga et al. 4 demonstrated the advantages of surgical treatment over conservative treatment for thoracolumbar burst fractures with no neurological deficits.The study showed an 8.2° average improvement of kyphosis in patients undergoing surgical treatment in contrast to about 4.1° worsening of kyphosis observed in patients treated conservatively.The result in the clinical assessment by the visual analogue scale of pain (VAS pain) was: 72 for conservative treatment, 87 for surgical treatment; "VAS spine": 61 for conservative treatment, 82 for surgical treatment; and RMDQ  (Roland-Morris Disability Questionnaire): nine for conservative treatment, three for surgical treatment, by which they conclude that surgically treated patients also showed better clinical outcomes.At the end of the treatment, 85% of surgically treated patients returned to work, whereas only 38% of the conservatively treated patients returned to work.Percutaneous pedicle fixation has been widely used as a complementary technique for lumbar fusion in degenerative pathology. 11In this study, the percutaneous pedicle fixation technique was used as a single fixation system of the AO type (A.3) thoracolumbar fracture.
In clinical evaluation, we used the Oswestry Disability Index and obtained a final average of 18% (minimal disability), better than the results published by Wei et al. 12 with a reported average of 34.1% (moderate disability).
The time of surgery (81 minutes) and blood loss (85 ml) were also lower than those reported in open pedicle fixation surgery, with a mean of 153 minutes and 828 ml, respectively, in the study by Verlaan et al. 13 The average correction of the Cobb angle was 8.2°, very similar to results published by Wen-Fei et al. 14 in a study of percutaneous pedicle fixation of thoracolumbar fractures without neurological deficits (with a mean Cobb angle correction of 8.9°) and the results published by Verlaan et al. 13 in a review of the surgical treatment of thoracolumbar fractures by classical transpedicular fixation (with a mean Cobb angle correction of 8.1°).
We can also see in our study that the results for the recovery of the vertebral body height (29.5%), recovery of the anterior wedging (17.1%), and of the spinal canal (14.6%) are identical to those published Wei et al. 12 in a study on thoracolumbar burst fractures with classical transpedicular fixation.
Regarding instrumentation without fusion, a prospective, randomized study compared pedicle instrumentation with and without fusion, 15,16 and demonstrated better results in the group without fusion.
However, some studies show that in AO type (A.3) fractures with a high degree of comminution of the vertebral body and high percentage of anterior vertebral wedging, pedicle fixation with fusion seems to have better results.Even in the absence of scientific evidence of the absolute necessity of fusion, specific instruments currently exist for percutaneous fixation that make fusion possible.

CONCLUSION
The percutaneous pedicle fixation technique presents radiological, clinical, and functional results that are significantly better than the published results with conservative treatment.
This intervention, assisted by fluoroscopy, proved to be a technique with a high accuracy and reliability, with results similar to those reported in studies with the classical transpedicular fixation regarding the deformity correction, but superior with regard to blood loss, postoperative rehabilitation, and return to the activities of daily living.
The results of this study show that this is a valid, safe, and effective treatment for (A3) thoracolumbar burst fractures without neurological deficits.

Figure 2 .
Figure 2. Preoperative CAT of a type L2 burst fracture: A) Sagittal, B) Coronal, C and D) Axial.

Figure 3 .
Figure 3. Surgical technique: A) Preoperative marking; B) Placement of the screws; C) Distraction after placement of the rod; D) Postoperative incisions.

Figure 5 .
Figure 5. Postoperative CAT of a type L2 burst fracture.A) Sagittal, B) Coronal, C and D) Axial.

Table 1 .
Demographics of the study population.